A method of carrying out a solid-liquid separation process of using a decanter-type centrifugal separator, mechanically separating a solvent oil from dehydrated slurry, and thus obtaining cake has heretofore been known (refer to Patent Literature 1, for example).
Patent Literature 1, however, refers only to the point of separating a solid and a liquid (a cake and a solvent oil) by using a decanter-type centrifugal separator.
When dehydrated slurry (solid matter quantity) supplied to a decanter-type centrifugal separator increases (when the dehydrated slurry is coal/kerosene slurry, the case corresponds to the case where the flow volume itself is large and the case where the concentration of the contained coal is high), it sometimes happens that the dehydrated slurry gets clogged in the middle of a flow channel. Otherwise, it sometimes happens that the flow state of the dehydrated slurry deteriorates and a chattering phenomenon (mostly vibration and rattle of a rotary shaft) occurs. As a result, it sometimes happens that the load acting on the decanter-type centrifugal separator increases, damages component parts such as a gearbox and a bearing, and deteriorates solid-liquid separation performance.